Biscuit spacing

[DPR]

I want to laminate 4 pieces of 2000x250x30mm hardwood (messmate) to make a table top. I'm using No20 biscuits and was going to place them in pairs (vertically).

I'm wondering what the spacing should be with each pair ie 7,8,7mm and how many pairs along the edge.

Any help would be much appreciated.

[Stubchain]

for my 2 bobs worth, I would put them 7mm from both sides, allowing for the buscuit this will give you about 7 or 8 mm gap in the centre. All nice and even. As far as how far apart probably 200mm.

[DPR]

Thanks that's about what I thought. However I was going to place the first pair 100mm in and then every 300 mm giving me bout 7 pairs in all.

[mat]

Don't sand the finished top too soon after gluing as the biscuits can push the surface above upwards and then it shrinks down again. If you sand too soon after gluing, the area over the biscuits may become sunken when the timber shrinks again.

Every 20cm is not necessary every 30cm is good enough but have the end ones closer to the end. I sometimes have to use a clamp at the ends over the joint line to push the two boards level. ie foot of clamp half on each board.

[Trav]

Long-grain to long-grain glueing (like you are doing) is a really strong join - even without the biscuits.

David Marks - the woodworking yoda - made a table top the other day on foxtel without using biscuits or dowels.

Biscuits are generally used to line the work up etc, not to add a great deal of strength.

I use biscuits pretty regularly and I think they are great. I would be inclined to go with one set abotu 100mm from each end, and then two or three more. Every 20 or 30cm is prob more than you need. But not going to hurt.

Trav

[Rocker]

Pairing the biscuits would definitely be overkill. I agree with trav that the sole function of biscuits in edge-joining is to assist with alignment. The joint will be strong enough without them. If the boards are dead straight, the biscuits can be further apart than is the case if the boards have a tendency to bow.

Remember to alternate the grain in adjacent boards, so as to minimize any tendency for the table top to cup.

Rocker

[Zed]

I wood make sure the would (heheheh) has at least 4mm from the top and the bottm of the bisquit hole. if the bisquit expands it could deform or crack the panel. bikkies are after all comlrpessed beech - whne it gets wet it expands into the joint you see......

cheers

[Wood Butcher]

for my 2 bobs worth, I would put them 7mm from both sides, allowing for the buscuit this will give you about 7 or 8 mm gap in the centre. All nice and even. As far as how far apart probably 200mm.

I have glued up large panels about the same size in the past and Stubchain's spacing is almost exactly the same as I used. The panels ended at a church for the desk in the office and far as I know there hasn't been a problem with movement at all. I wouldn't place the biscuits any closer to the edge as if there is any fine cracks in the timber, the swelling of the biscuits could cause a crack to appear.

Rowan

[aabb]

Pairing the biscuits would definitely be overkill. I agree with trav that the sole function of biscuits in edge-joining is to assist with alignment. The joint will be strong enough without them. If the boards are dead straight, the biscuits can be further apart than is the case if the boards have a tendency to bow.

Remember to alternate the grain in adjacent boards, so as to minimize any tendency for the table top to cup.

Rocker

I agree totally with above and Trav's comments. Also when clamping to not over tighten as this could lead to cupping too. Suggest you clamp a couple of slats across width of top (on top and bottom) to assist in preventing cupping.

Albert

[Harry72]

I wouldnt bother with the biscuits at all, just make sure the boards are jointed nicely and clamp it up with many cauls to keep it flat while the glue sets.

[Richardwoodhead]

Like most are saying, what you're planning is way way too many biscuits. You can get away without any. But, I like to use them for easy alignment. (I've found using biscuits helps in quickly achieving a good flat table top. AS LONG AS YOU ALWAYS biscuit from the same face edge e.g, top surface). All you need are one at each end (about 100 mm in from each end) and the rest about 300 mm apart. And NOT doubled up in pairs!

Richard

[DPR]

Thank you all for your valuable help. I've now used 7 biscuits - the end 2 100mm in and then at 300mm intervals. I've clamped up and down with 6 clamps, clamped the ends, alternated the grain and clamped slats acoss top and bottom. Phew I think it should hold!

David

[harcx]

I wouldnt bother with the biscuits at all, just make sure the boards are jointed nicely and clamp it up with many cauls to keep it flat while the glue sets.
I think you're right about the need for biscuits but I thought I'd toss in a comment about the need for jointing
Many moons ago there was a cedar furniture workshop in Greenhills just west of Kempsey and the had a technique for edge jointing that resulted in the most invisible joints I've never seen.
They had a wide bed table saw with the blade pretty much in the centre and would make a very fine cut off one edge of the one piece the timber to be joined and, on the reverse side of the blade, take a similar cut off the mating piece.
This formed two mating faces with very similar saw marks abutting (the trick being to feed the stock through at the same pace on the two cuts). They would then "rub" the faces together so the patterns interlocked and clamp etc as normal
After finishing you were very hard pressed to find the joint and I still have a piece they made30 years ago with a perfect joint .
I've tried to replicate on my Triton but either me or it is not up to the task. One day ....
Cheers
HarcX

[mat]

I don't have a jointer so I use a router with a straight bit and run the router base along a straight edge (thick aluminium angle) clamped at the appropriate distance from the edge of the board. You can also clamp the aluminium angle under the board edge and use a router bit with bearing.

A foolproof way to counteract any wave in a straight reference edge used is to place the two edges to be joined just less than a straight router bit diameter apart secure by any means including tacking to a rail underneath, set the straight edge at the appropriate distance from the "slot" and run the router down the slot. Any variation in straightness is counteracted by routing both edges at once.

[Termite]

Regardless of what machinery you use for edge preparation, IMO nothing beats a final lick with a sharp plane for near invisible edge joining.